Interferon is an endogenous protein which plays an important role in mammalian immune system, takes a part of nonspecific defensive mechanism in vivo and greatly participates also to specific defensive mechanism in vivo. In fact, interferon has been used in the clinical field as a therapeutic agent for viral diseases, such as hepatitis B and C, etc. Low molecular weight organic compounds which induce biosynthesis of said interferon (interferon inducers) have been developed as an interferon preparation in next generation. Imidazoquinoline derivatives (see European Patent Publication A 145340), adenine derivatives (see WO 98/01448 and WO 99/28321), etc. are illustrated. For example, Imiquimod, an imidazoline derivative is used in the clinical field as an external antiviral agent for genital verruca.
By the way, T cells which play the key role of the immunological response in vivo are classified into two kinds, Th1 cells and Th2 cells. In the body of patients suffering from allergic disease, cytokines such as interleukin 4 (IL-4), interleukin 5 (IL-5), etc. are excessively secreted from TH2 cells and therefore, it is expected that the compound which suppresses immune response of Th2 cells becomes a therapeutic agent for allergic diseases.
It is known that the above imidazoquinoline derivatives and adenine derivatives have not only the interferon inducing activity, but also have the activity suppressing the production of interleukin 4 (IL-4) and interleukin 5 (IL-5). In fact it is known that these derivatives are effective for allergic diseases on animal model.
However, there is anxiety for systemic adverse-effects due to the interferon inducing activity such as fever, interferon-like diseases when these derivatives are administered as an antiallergic agent.